Why have they selected your appointment for this purpose of forgery??
You are not manager HR,you are not purchase officer?
What reason could be there in making you a scapegoat?
This needs to be discussed with a legal consultant for legal actions before they land you into problems.
After taking legal opinion/inputs write to the management about the whole issue.
Keep facts documented and also sent to appropriate authorities under acknowledgment.
Your documenting these facts will keep your side legally safe.